[mr67gp]

I have searched a couple different ways and found nothing here that described installing a GV OD unit in a '65-'70 full size. I am doing my homework on putting one in my '67 GP HT behind the TH400. I would also install the 3.42 Saf-T-Trac I have in place of the 2.93 unit it has now. The ratios work out quite nicely with a 27" tire.

The question is, what spacer would be most appropriate to use? It appears there are three different versions available from GV, "shorty", 4" and 9".

I have no issue with getting the drive shaft shortened, just looking for feedback from others that have BTDT.

Thanks.

[mr67gp]

I'm surprised nobody has done this. I guess I'll be the guinea pig . . .

[Singleton]

It all depends on which TH400 you currently are using, the short tail 400, or the long 400. Since its a big car, I assume its the long tail th400, and you will need the long adapter from GV. What you calling a spacer is an adapter that replaces the tail shaft housing on your th400.

[Sirrotica]

I haven't done the swap, but I have researched what you're trying to do. After researching OD options, the GV unit takes up way more real estate than just converting to a 4L80E does. The first picture is a 4L80E, second picture is T400 with GV bolted on.





The research I did mentioned having to make some floor/tunnel modifications to get the GV unit to clear in a 67 lemans. After researching the two options I decided for my own purposes the 4L80E was a better alternative than a GV add on.

The 3.42 will work well with the 4L80E, my 05 GTO has a 3.46 with a 4L60E and it is the best ratio for what I use the car for.

[ScottP]

Have you given any thought to trying a 4L80E instead of the GV unit?

I'm running a 4L80E in my 70 Bonneville with a 3.55 Saf-T-Trac rear and 28"
tall tires (235/60R17). I'd be hard pressed to oversell just how much I love this
combo. I swapped this in place of a TH400 and 3.23 setup. The floorpan of
the '65-70 fullsize cars accepts the 4L80E with ease.

There are of course loads of arguments to be made for all the different OD
options out there - 700R4, 200-4R, GV, etc...., but my vote is 4L80E all day long.

-Scott

[mr67gp]

Yep - '67 GP, long tail TH400

I looked into the 4l80e and thought the GV unit would be simpler, since I would need an adapter and stand alone controller for the transmission. Cost was about the same to a bit less for the GV route.

I have no specific objection to the 4l80e, and it would accomplish the same goal, just would remove the original trans, rather than adapt it.

[Stuart]

A TH200-4R overdrive transmission can be had with a BOP bolt pattern, that may be another option to consider. I've heard arguments either way about how one will hold up behind a Pontiac engine, but it would seem these days you should be able to get one built to withstand high torque and horsepower levels.

[Chief of the 60's]

200's are the worst choice for a reason. Nothing but failure. That is why GM only made them for a few years and they never went into any heavy duty application. The hardest work they ever did was 276 horse in a GNX which did not come in at the hit of the throttle and still blew up. Today, you need to spend about $3000.00 to have one built that may last.

[mr67gp]

Yeah, I'm not going the TH200 route. The 4L80 will hold up, but I am not sure the extra work for the speedo drive, TPS, and TCU are worth the effort to get an extra couple hundred RPM drop from the lockup converter. I need to do some more homework on the room I need in the tunnel for the GV unit. Length is not an issue, obviously, but I don't want to make substantial changes to the tunnel to fit the unit.

[Ben M.]

The GV unit is not an insignificant investment and last I looked they still wanted you to change the transmission fluid at the same interval as your engine oil.

The standalone controller and speedometer adapter are annoying but you get a better package in the end with the 4L80E.

[stevep]

What are you trying to achieve? More power off the line and good cruising RPM?
Is it a cruiser or are you running it down the track?

A GV unit is probably $3500 by now.

[Sirrotica]

Originally Posted by Ben M.

The GV unit is not an insignificant investment and last I looked they still wanted you to change the transmission fluid at the same interval as your engine oil.

The standalone controller and speedometer adapter are annoying but you get a better package in the end with the 4L80E.

Add to the fairly high maintenance of this unit to the fact if it breaks GV requires you to send it back to them for repairs, they do not sell repair parts to the general public. They also have a monopoly on parts as I have never been able to find another source for internal parts.

The original manufacturer of the unit is Leycock de Normanville in the UK and GV purchased the rights to the unit and spare parts that Laycock de Normanville had. Laycock de Normanville made this unit for many for MG and other British made cars, the last major user of the unit was Volvo which used the unit on their production cars in 75-86.

[Ben M.]

Originally Posted by Sirrotica

Add to the fairly high maintenance of this unit to the fact if it breaks GV requires you to send it back to them for repairs, they do not sell repair parts to the general public.

Yup. I used to drive by their facility all the time and they won't even answer the door much less let you in to talk about repairs or sell parts. It has to go back to them complete in the mail and you're footing the bill.

It's not a bad system, but it is as you said, a one of a kind system that they have the market on. Some people don't mind this, but it's something to be aware of.

[lust4speed]

Pay all that money for the Gear Vendors and then still have to freshen up the T400.

[Stuart]

Originally Posted by Chief of the 60's

200's are the worst choice for a reason. Nothing but failure. That is why GM only made them for a few years and they never went into any heavy duty application. The hardest work they ever did was 276 horse in a GNX which did not come in at the hit of the throttle and still blew up. Today, you need to spend about $3000.00 to have one built that may last.

Still sounds like it may be less expensive than going with the Gear Vendor unit, and for a street driven car that isn't raced I think it's an option worth considering. It will bolt up to a Pontiac block, and it's about the size of a TH350 so there won't be space issues in the transmission tunnel. I understand that in stock form they weren't that strong, and I admit I have no personal experience with them, but from what I've read there's a lot that can be done today to beef up the TH200.

[mr67gp]

Originally Posted by stevep

What are you trying to achieve? More power off the line and good cruising RPM?
Is it a cruiser or are you running it down the track?

A GV unit is probably $3500 by now.

Hey Steve,

Your summary is about right, with the added caveat that I would prefer to leave the car reasonably unmolested. The electronically controlled transmission options require changes not required by the GV unit. I want to be able to drive the car longer distances at highway speeds, but also enjoy the kick in the ass that the 428 and a 3.42 will give me. No track duty for this one.

Current GV pricing is about $2800, plus the drive shaft modification cost.

The maintenance regimen for the GV unit is really a non-issue for me.

Freshening/updating a TH400 is not a significant challenge for me, and would have to be done with a used 4l80 too that I did not know the history on.